I think before you ask the questions you need to have a good idea of what you want from the minder?
Do you want a minder who is experienced or fairly new. a youngish or older minder.
minder with or without pets. do you want a minder who has several children on roll or a less busy minder. a minder who is out and about lots or one who isn't.
what's your expectations of a minder?
what do you know about minders?
its always good to go in with these sorts of things in mind.
Things to look for:
ask to see their certificate of registration and any others - training inclusive of first aid and insurance.
How well the minder interacts with you and more particuarly your child
There should be a good range of (acessable) toys and equipment - alhtough this is not an indicator as they may have stuff stored away or to get if they do not have that age group currently.
is the Setting clean and safe. not necessarily tidy but safe tidy
Things i would ask:
What will my child be doing in a day/week with you?
What sort of places will you be taking my child to?
What are their views on behaviour management/ tv/meals/time-snacks/
Ask to see the policies and procedures, Ofsted report, references, can you come back during workiing hours
I would want clarification of fees - bank and public holidays, their holidays and time off, clarification of fees for unintended late pick ups
so much of it goes on the 'feel' and gut instinct. Don't be afraid to ask if you want to know more or don't understand. A good minder should be open, honest, give you enough info.